The present invention relates to a heat exchanger, in particular, to a fin of a heat exchanger which is used at a location replete with sand dust, or used in a heat exchanger in which an exhaust gas of an engine circulates, and a heat exchanger in which a granulous substance of dust or the like is difficult to adhere to a surface of the fin.
The most effective method for improving the performance of a heat exchanger resides in forming a number of louvers at a surface of a fin by cutting to raise the surface.
However, according to a heat exchanger which is used at locations full of dust, or a heat exchanger in which an exhaust gas of an engine circulates, clogging is brought about at the louver, and a fin efficiency is rapidly deteriorated.
Hence, there are known various kinds of fins which are formed with recesses and protrusions or convex shapes of wave forms at surfaces of fins in place of the louver fins.
As an example thereof, Patent Document 1 described below has been proposed. According to the proposal, as shown by FIGS. 9A and 9B, a surface of a fin arranged between tubes is alternately formed with a number of W-shaped convex portions and concave portions, and a traverse section thereof is formed in a wave form. Further, angles of continuous lines of ridge portions or valley portions of the waves fall in a range of 10 degrees through 60 degrees relative to a principal flow of air. In addition, folded lines of the W in line with the principal flow of air are formed symmetrically in a left and right direction.
Further, as shown by FIG. 9A, the air flow circulates in an arrow direction relative to the W-shaped wave. Then, a number of vortex flows in directions different from each other are produced in the air flow.
Next, it is also thinkable to form a wave in a V-shape as shown in FIG. 4A by adopting a portion of the wave in the W-shape. In this case, four uniform vortex flows are formed inside each segment of a fin. The vortex flows contiguous to each other are respectively formed in directions reverse to each other.
In FIG. 4A, inclined convex portions 2a and 2b forming a V-shaped convex form are formed in angles symmetrical with each other in a left and right direction relative to a center of the air flow 5. That is, the inclined convex portion 2a on the left side makes an angle α relative to a center line and the inclined convex portion 2b on the right side makes a minus angle α.    [Patent Document 1] WO2008/090872A Publication